The present invention relates to an ink-jet cartridge for being used for a thermal ink-jet printer, and more particularly to an ink-jet cartridge containing a back pressure-adjusting device therein for being used for a thermal ink-jet printer.
Currently, three kinds of printers, i.e. dot-matrix printer, thermal ink-jet printer and laser printer, are commercially available for adapting to be used for a computer. In spite of that a dot-matrix printer has an advantage of the lowest price among them, which has the disadvantages of the slowest printing speed and the most inferior printing quality among them. Although a laser printer has an advantage of the best printing quality among them, which, particularly for a color laser printer, has the disadvantage of the highest price among them. Therefore, up to the present, the thermal ink-jet printer is the most popular one for the general public.
Please refer to FIG. 1 which is a schematic diagram illustrating a structure of a conventional ink-jet cartridge 10 adapted to be used for a thermal ink-jet printer. Conventionally, an ink-jet cartridge 10 includes a housing 11 for storing the ink 13 in an interior 12 thereof, and a printhead 14 having a plurality of orifices (not shown) thereon for allowing the ink 13 to be jetted therethrough when the thermal ink-jet printer is printing. According to the ideal-gas law,
PV=nRT
where P: pressure, V: volume, n: mole number of the gas molecules, R: ideal-gas constant, T: temperature
xe2x80x83if the temperature is maintained at a constant value, the pressure would inversely change with the volume. Certainly, when the thermal ink-jet printer is printing under the environmental temperature, the volume of the space 121 unfilled with the ink 13 will gradually increase because of consumption of the ink 13. That is, if the volume of the space 121 unfilled with the ink 13 increases when the thermal ink-jet printer is printing, a back pressure of the space 121 would lower simultaneously. On the other hand, if the environmental changes, the back pressure of the space 121 might change as well. Once the back pressure changes, it might be so easy or so hard for the ink 13 to be jetted through the orifices and therefore the printing quality is influenced.
Please refer to FIG. 2(a) which is a schematic diagram illustrating another structure of a conventional ink-jet cartridge 20 adapted to be used for a thermal ink-jet printer. Comparing the ink-jet cartridge 20 of FIG. 2(a) with that of FIG. 1, in addition to a housing 21 for storing the ink 23 in an interior 22 thereof and a printhead 24 having a plurality of orifices (not shown) thereon for allowing the ink 23 to be jetted therethrough when the thermal ink-jet printer is printing, the ink-jet cartridge 20 further includes a hollow tube 25. Preferably, a diameter of the hollow tube 22 is ranged from 0.5 to 2.0 mm. The hollow tube 22 is used for regulating the back pressure of the space 221 by a capillary action of the ink 231 contained in the hollow tube 25. Even if the volume of the space 221 increases when the thermal ink-jet printer is printing, the back pressure of the space 221 would not lower. However, as shown in FIG. 2(b), when the ink-jet cartridge 20 is inverted unwarily during transportation, owing to the low value of the surface tension of the ink 231 contained in the hollow tube 25, it is easy for the ink 231 to flow out of the hollow tube 25 or the atmosphere 26 might pass into the hollow tube 25 such that the back pressure of the space 221 unfilled with the ink 231 will not be controlled at a desired suitable range any more. Although a much thinner hollow tube, which provides a higher value of the surface tension of the ink 231 contained in the hollow tube 25, can be provided to solve the problem, the yield for manufacturing such a much thinner hollow tube is so low that the manufacturing cost thereof is very high.
Accordingly, it is attempted by the present applicant to overcome the above-described problems encountered in the prior arts.
An object of the present invention is to provide an ink-jet cartridge containing a back pressure-adjusting device therein for being used for a thermal ink-jet printer.
Another object of the present invention is to provide an easily-manufactured back pressure-adjusting device of an ink-jet cartridge for being used for a thermal ink-jet printer.
According to the present invention, the ink-jet cartridge adapted to be used for a thermal ink-jet printer is disclosed. The ink-jet cartridge includes a housing for storing the ink in an interior thereof, a printhead having a plurality of orifices thereon for allowing the ink to be jetted therethrough when the thermal ink-jet printer is printing, and a pressure-adjusting device disposed in the housing for regulating a back pressure of the interior of the housing, wherein the pressure-adjusting device includes a first opening fixed on an upper portion of the housing and exposed to an ambient atmosphere, and a second opening disposed at a bottom of the interior of the housing and having at least one regulating hole thereon, wherein the regulating hole has a cross-sectional area being smaller than that of the first opening for maintaining the back pressure when the ink-jet cartridge is inverted.
Preferably, the back pressure of the interior of the housing is regulated by a capillary action of the ink contained in the pressure-adjusting device.
Preferably, the second opening of the pressure-adjusting device is fixed at the bottom of the interior of the housing.
Preferably, the second opening of the pressure-adjusting device is hung over the bottom of the interior of the housing.
Preferably, the pressure-adjusting device is a hollow tube.
Preferably, a diameter of the hollow tube is identical except a portion adjacent to the second opening.
Preferably, the diameter is ranged from 0.5 to 2.0 mm.
Preferably, the hollow tube is made of stainless.
Preferably, the second opening is pressed such that one regulating hole is formed thereon and the second opening is plane-shaped in cross-section.
Preferably, the second opening is pressed such that a plurality of regulating holes are formed thereon.
Preferably, the pressure-adjusting device is made of plastic.
Preferably, the pressure-adjusting device is formed by injection molding.
Preferably, the pressure-adjusting device is integrally formed with the housing by injection molding.